1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, particularly to an electrophotographic photosensitive member having a photosensitive layer containing a novel azo pigment.
2. Related Background Art
Heretofore, electrophotographic photosensitive members utilizing inorganic photoconductive members such as selenium, cadmium sulfide, zinc oxide, etc. have been known.
On the other hand, since discovery of specific organic compounds which exhibit photoconductivity, a large number of organic photoconductive members have been developed. For example, there have been known organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, etc.; low molecular weight organic photoconductive members such as carbazole, anthracene, pyrazolines, hydrazones, arylalkanes, etc.; or organic pigments or dyes such as phthalocyanine pigments, azo pigments, cyanine pigments, polycyclic quinone pigments, perylene type pigments, indigo dyes, thioindigo dyes or squaric acid methine dyes, etc.
Particularly, organic pigments or dyes having photoconductivity can be synthesized more easily as compared with inorganic materials. Further, flexibility capable of selecting a compound exhibiting photoconductivity at a suitable wavelength region has been expanded. Therefore, a large number of photoconductive organic pigments and dyes have been proposed. For example, there have been known electrophotographic photosensitive members by use of azo pigments exhibiting photoconductivity as the charge generation substance in the photoconductive layer which is separated into functions of the charge generation layer and the charge transport layer, as disclosed in U.S. Pat. Nos. 4123270, 4247614, 4251613, 4251614, 4256821, 4260672, 4268596, 4278747 and 4293628.
Also, azo pigments as disclosed in U.S. Pat. Nos. 4279981, 4352876, 4356243, 4390611, 4418133, 4436800, 4439506, 4447513, 4471040, 4495264, 4551404, 4571369, 4582771, 4599287 and 4600674 have been known as the charge generation substance in the photosensitive layer.
Since the electrophographic photosensitive member by use of such organic photoconductive members can be produced by coating by selecting suitably a binder, they have the advantages such that photosensitive members can be provided with extremely high productivity at low cost, and yet that the photosensitive wavelength region can be freely controlled, and therefore practical application thereof is under rapid progress in recent years.
However, such photosensitive members of the prior art can not be said to be satisfactory with respect to sensitivity and repetition characteristic, and most of their uses are limited to low grade electrophotographic copying machines, etc. under the present situation.